Stereoscopic apparatus.



G. BALMITGERE.

sTERBosGoPIc APPARATUS.

APPLICATION FILED MAY 14, 190B.

1,105,395. Patented July 28, 1914.

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y gy y G. BALMITGIJRB.

STERBOSOOPIC APPARATUS.

APPLIUATION FILED MAY 14, 1908.

1,105,395, Patented July 28,1914,

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.pointed out in the claims.

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eyes use is made of the stereoscope, which manner stereoscopes have beenconstructed GEORGES BALMITGRE, OIF PARIS, FRANCE.

STEREOSCOPIC APPARATUS.

Specification of Letters Patent.

Patented July as, 1914.

vApplication led May 14, 1908. Serial N o. 432,808.

To all whom fit may concern Be it known that I, GEORGES BALMITGRE, of 2Rue Philippe de Girard, in the city of Paris, Republic of France, haveinvented a Stereoscopic Apparatus, of which the following is a full,clear, and exact description.

This invention relates to stereoscopy and the principal object of theinvention is to provide a novel stereoscope for reproducing stereoscopicviews, so that the impression of relief can be reproduced withoutnecessitating the material inversion of the views.

` The invention consists in the novel construction and combination andarrangement of pai-ts as is hereinafter described and Reference is to behad to the accompanying drawings forming a part of this specification,in which- Figure l represents two images obtained upon a single plate,forreproductionin the stereoscope; Fig. 2 is a front view of a form ofstereoscope according to t-he present invention; Fig. 8 is a sectionalViewV of the is a plan view of the same; Fig. 5 is a sectional view onthe line D-D of Fig. 4; Fig. 6 is a sectional View on theI line EE ofFig. 4; Fig. 7 is a sectional view on the line F--F of Fig. l; Fig. 8 isa detail View of the mirror shown in Fig. 3; and Fig. 9 is a sectionalView of a modified form of stereoscope.

It is universally known that to reproduce the impression of reliefa'iforded by both allows two photographs of the same subject, taken with'a camera provided with two lenses, to be condensed into a single image,the aforesaid lenses being separated by a distanceequal to t-he normaldistance apart of the eyes or differing slightly from this distance.Stereoscopic cameras have been constructed in sucha way thatthe twoimages were produced by two lenses havingy identical principal focaldistances; in like having eye pieces of the same focal length.

The presentinvention consists of a stereo-V scope arranged to re roduceviews taken by a camera in which lenses are used having principaldistances which are perceptibly unequal, the stereoscope being soarranged that. the images willbe placed at distances m and y from theoptical centers ofthe eye pieces such that the ratio will be equal tothe ratio between the principal focal distances of the lenses of theapparatus, the eye pieces having then either focal distancesapproximately equal respectively to' and 'J or greater focal distancesand determined in such manner that both images will be seen in thespacel under the same angle and in the saine plane. In particular theeye pieces of the stereoscope may have principal focal distances whichare respectivelequal to the principal focal distances ofy t of thecamera; these lenses may finally themselves serve as eye pieces for thestereoscope. Thus for example, let it be supposed that two photographicimages of the same object are taken under the above conditions with twolenses placed a distance apart approximately equal to the distance apartnormally of bot-h eyes and having respectively principal focal distancesof 5 and 10 centimeters, this last one being placed to the right of theother; if the left eye looks at the image taken with the left hand lensthrough a converging lens having a principal focal distance equal to 5centimeters, it will see the object in its normal size, according to awell known principle; the right eye will likewise see this object in itsnormal Size if it looks at the image taken with the right hand lensthrough a lens of l0 centimeters principal focal distance. The twoimages being seen at the same time of normal size will condense, givingthe illusion of relief. In

the above example the images are supposed to be placed at the focus ofthe lenses.

A sterecscope made according to this invention has various advantages,the principal of which is, if the two views necessary to produce therelief are taken on a single plate, of being able to reproduce theimpression of .relief Without necessitating the inversion of the views(which inversion of the views is indispensable in ordinary stereoscopes)so that the negative can be seen in relief as soon as it is finished,that the taking ot of the positive can be effected in a single exposureto light without necessitating the separation of the two negativeimages. The black and colored positives directly obtained in the darkroom can be utilized immediately without any modification, the defectsof register so frequent in ordinary stereograms are completely obviated,and finally these advantages can be obtained without the help 4of prismsor mirrors in the photographic apparatus which is a very importantfeature.

he lenses The two views to be reproducedin the stereoscope are ofdiderent sizes and may be obtained upon the same plate by the employmentof a suitably arranged carriera..I `Flgen-y taken |upon a single platerepresented by way of example in Fig. 1, the images are inverted, asupon the negatives of stereoscopic apparatus of the ordinary kind; forexample the smaller image ltaken withl the left hand lens may be lookedat 'so that it shallbe on the left of the larger image, but the lefthand edge of this small image represents the right hand edge of thesubject photographed; it is necessary therefore in order to reestablishthe exact position while yet maintaining the small image on the left ofthe large one, to cause this small image to rotate in such a Way as tobring to the left the right hand edge which should nor; mally besituated there; the same operation must be performed for the largeimage. This turning around with the prints of ordinary stereoscopicapparatus requires the separation of the two images or the printing intwo operations with special frames; it takes place on the ycontraryautomatically,

' when the images are arranged as shown in Fig. 1, by the aid of thestereoscope made according to this invention having the generalarrangement indicated by way of ex-.

ample in Figs. 2, 3', 4, 5, 6, 7. lin these ligues, e and f are the eyepieces, separated by a distance approximately equal to the distanceapart normally of the eyes; -p is an opening through which the plate abearing the double print (positive or negative) is introduced into thestereoscope; q is a mirror intended to reect the light onto the plate a;this mirror may be fixed to the box of the stereoscopeby a hinge, asshown in Figs. 3 and 4; this mirror ishowever not indispensable and maybe omitted; the plate n, is held in by vertical grooves 7' and s; itrests upon the lower panel of the stereoscope in a groove t, in such aw'ay that lthe center of each of the images is situated in the hori-v4zontal plane containing the optical axes of the eye pieces, that is tosay, in the plane 'Cf-C (see Fig. 2); aand o4 are openingsVcorresponding to the dimensions vand to the position of the two images'of the double print; the heights of these openings are t'o each otheras the bases of the openings; w and y are mirrors Ain which the largeand the small images respectivelyare reflected; these mirrors arearranged in such a Way that the planes containing the virtual images areperpendicula'rjto the `optical axes of the eye pieces, these opticalaxes being also parallel to each other; furthermore, the position ofthese mirrors is so combined with the position and the dimensions of theother elements of the stereoscope that: 1st, the cen- 'ter of each ofthe virtual images is approxi# mately in alinement with the optical axisi :leases of the corresponding eye piece; 2nd, the ratio between thedistances of each virtual image to the optical center of thecorrespondingeye piece is equal to the ratio between the principal focaldistances of the lenses of the camera in which the plates. werephotographed. The principal focal distances of the eye pieces are theneither equal respectively to the above-said distances or calculated ashereinafter described.

The expression center of an image hereinabove used and to be usedhereinafter, in-r dicates the point of the image which was situated inthe photographic apparatus, in alineme'rit with' the optical axis of thelens which served to obtain it.` 4

The mirror y, corresponding to the small image, may be of the form shownin Fig. 8,

so as to enable the edge of the eye piecef to be flush with the mirroras shown in Figs. 3 and 7. y

Asthe eyepieces of the stereoscope shown in section in Fig. 3 mustnecessarily be separated by a distance approximately equal to the normaldistance 'apart of the eyes, it is easy to understand that in order thatthe condensation of the two images (see Fig. l) may be easily eected inthe stereoscope, the dimensions of the di'erent elements of thestereoscope and of the corresponding stereoscopic camera are notabsolute but vary in particular with the ratio between the homologousdimensions of the two images.

The dimensions of these elements may be obl the width of the small.mirror'y has been re` 105 duced on' the side ont' the images, so as notto prevent the right eye from viewing vthe partof the large imageadjacent to the small one; an opaque screen 44 moreover prevents theleft eye from viewing the large image; Fig. A

9 shows also that a sheet of ground glass 45 hasbeen placed behind theplate carrying the images. `In the same manner as in the stereoscopeshown in Fig. 3, the' parts of the stereoscope shown in Fig. 9 are so'arranged 115 .that theratio between the distances oit' tl'e virtualimagesto the optical centers of the corresponding eye pieces will beequal to the ratio between the focal distances of thle lenses of thestereoscopic apparatus and accoi-ding to the homologous dimensions ofthe images. Then,if the focal distances of the In order to see theseimages as if they were placed at` a nearer distance, the eye pieces willbe given. greater focal distances. These focal distances can beascertained by a tentative method or by means of formulae used inoptics.

In order to compensate the difference of perspective which may occur inthe case of the photography of very near objects, the mirrorcorresponding to the small image can be so arranged that the verticalplane containing the small virtual image will be slightly inclinedrelatively to the vertical plane containing the optical axes of the eyepieces so that the straight edge of the small virtual image will be alittle nearer to this plane than the left edge; the same results can beobtained by modifying in a reverse manner the position of the largestmirror.

Any suitable device, screw, tappet, ete), can be employed for a justinthe mirrors at will from the outside of t e apparatus.

As the eye'pieces give a greater distortion when the focal length isshort, the lens corresponding to the small image can be so chosen as togive a reverse distortion. The eye pieces of the stereoscope can bemade' adjustable in and out at will, the adjusting means, which may beof any suitable kind, being so arranged that the ratio between thelengths of displacement of the eye pieces will always be equal to theratio between the `homologous dimensions of the images.

.In the above description it has been supposed that the smaller of thetwo images to be reproduced in the stereoscope was taken on the left ofthe larger image but it is quite evident that the reverse order may beadopted.

I claim:

l. A stereoscope for viewing views composed of two images of differentsizes, the said stereoscope having eye pieces of different focallengths, means for supporting the views in the stereoscope in an obliqueposition relatively to the optical axes of the eye pieces, and means forstraightening the images, the said eye pieces being so arranged that theimages appear of the same size and at the same distance.

2. A. stereoscope for viewing the views composed of two images ofdifferent size upon a single plate, the said stereoscope having meansfor supporting the plate in the stereoscope, in an oblique positionrelatively to the optical axes of the eye pieces, and refiectingsurfaces placed in reverse direction obliquely to the optical axes forstraighten ing the images, the eye pieces being arranged so that thevirtual images produced by the refiecting surfaces appear 1n .the samesize at the same distance.

3. A stereoscope for viewing views composed of two images of differentsize upon a single surface, the said stereoscope having eye pieces ofdifferent focal lengths, means for supporting the views in an obli ueposltion relatively to the optical axes o the eye pieces, thestereoscope having openings in its wall corresponding to the dimensionsand to the position of the two images of the view, and mirrors placed inreverse direction obliquely to the optical axes for straightening theimages, the eye -pieces being arranged so that the virtual lmagesproduced by the mirrors appear of the same size and at the samedistance.

The foregoing specification of my method of stereoscopy and apparatusfor the apitlication of this method signed by me this st day of May1908.

GEORGES BALMITGRE.

Witnesses:

DEAN M. MASON, MAURICE H. PIeNE'r.

